Flower

Flowers are the specialized reproductive structures of angiosperms, which are plants that produce flowers. Their primary biological purpose is to facilitate reproduction and ensure the survival of their species. Through complex processes, flowers produce sex cells and help disseminate seeds across different environments. This reproductive effectiveness allowed flowering plants to eventually replace many non-flowering plants in various ecosystems. Today, flowering plants dominate the majority of the world's ecosystems, ranging from tiny orchids to massive trees.

The morphology, or physical structure, of a flower can be divided into two main categories. The vegetative part, known as the perianth, consists of non-reproductive structures. This includes the calyx, which is made of sepals, and the corolla, which is made of petals. The reproductive or sexual parts include the male and female organs. All these structures grow from a thickened part of the flower stalk called a receptacle. The stalk itself is known as the pedicel.

Within the perianth, the sepals and petals serve distinct roles. Sepals are modified, leaf-like structures that form the outermost whorl, called the calyx. They are often waxy and tough to protect the flower during its development. Petals form the next whorl, known as the corolla. They are often delicate, thin, and brightly colored to attract pollinators. Some petals even show patterns visible only under ultraviolet light. These patterns are invisible to humans but are seen by many pollinators.

The reproductive process relies on the androecium and the gynoecium. The androecium is the whorl of male parts called stamens. Each stamen typically consists of a stalk called a filament and an anther. The anther contains microspores that develop into pollen, the male gametophyte. The gynoecium is the innermost whorl and serves as the female part. It consists of one or more carpels, which include a stigma to receive pollen, a style, and an ovary. The ovary contains ovules, which house the female gametophytes.

Reproduction begins with pollination, the movement of pollen to the female parts. This can occur through cross-pollination between different plants or self-pollination within the same plant. Pollen is moved by living things like insects and birds, or non-living things like wind and water. Plants often favor cross-pollination because it increases genetic diversity. After pollination, fertilisation occurs when the male and female sex cells fuse. This fusion triggers the development of a seed through cellular and nuclear divisions.

As the seed develops, the flower undergoes significant changes. The female part of the flower often transforms into a fruit. The fruit serves to protect the developing seed and assist in its dispersal. Seeds can be spread by wind, water, or animals that eat the fruit. For example, a bird might eat a fruit and distribute the seeds through its waste. While the fruit and seeds develop, the other floral structures usually die off.

Flowers exhibit immense diversity in size, shape, and symmetry. They can range from the tiny duckweed to the massive corpse flower. Some flowers show radial symmetry, meaning they look the same from any side. Others have irregular symmetry, which often helps them coevolve with specific pollinators. Some species are perfect, meaning they have both male and female parts. Others are unisexual, meaning they have only one sex. If male and female flowers are on one plant, it is monoecious. If an individual plant is only one sex, it is dioecious.

Humans have interacted with flowers for thousands of years. We use them for medicine, food, perfumes, and decoration. They also hold deep symbolic meaning in art, literature, and religious rituals.

Beyond individual flowers, many plants grow in clusters called an inflorescence. Some clusters, like those in sunflowers, are actually many tiny flowers called florets. These are known as pseudanthia, where a group of flowers looks like a single large bloom.